1. Field of the Invention
This invention relates to reductive bleaching formulations containing glucose, nonionic surfactants and buffer salts, to a process for the alkaline bleaching of dyed cotton fabrics and to the use of the formulations as reductive bleaching agents.
2. Discussion of Related Art
The annual world production of jeans amounts to several million pairs. A large part of this total is subjected to an artificial ageing process in which the jeans are treated together with stones in a wash liquor so that they assume a "worn" appearance, but at the same time are made softer and hence more comfortable to wear. In addition, the statistical washing out of color associated with the worn appearance is often desired by the consumer ("stonewash effect"). Another consumer demand is similarly directed, i.e. to bleach the fabric and to give it a used appearance. To this end, the fabric is generally treated with alkaline hypochlorite liquors or hydrogen peroxide. Although the bleaching agents mentioned are extremely effective to use, they also have serious disadvantages. Thus, the use of hypochlorites leads to very considerable AOX pollution of the wastewater while the use of hydrogen peroxide, particularly in the form of concentrated solutions, is only possible with considerable outlay on anti-explosion measures. In addition, both hypochlorite and hydrogen peroxide not only bleach the fabric, they also cause non-selective damage so that, in the course of bleaching, 10-15 pairs of blue jeans out of 100 generally have to be rejected.
DE-A1 4306827 (Rotta) describes a process for bleaching textiles, preferably denim, treated with vat dyes in which glucose in the form of an alkaline solution is used as reducing agent. Although the reject rate can thus be distinctly reduced in relation to the treatment with hypochlorite, the result obtained is still not entirely satisfactory. In addition, the lightening in color and, in particular, the softness of the fabrics are unsatisfactory.
Accordingly, the problem addressed by the present invention was to provide bleaching agents which would not have any of the disadvantages mentioned above.